The influence of the ultrasound characteristics on the electrodeposition of copper from chloride-based electrolytes

Abstract

• Electrochemical quartz crystal microbalance (EQCM)-coupled ultrasonic technique to monitor Cu deposition/dissolution behavior. • Strong influence of the ultrasonic intensity on the behavior of Cu deposition/dissolution from the chloride-based electrolyte. • Rapid random change in the surface ion concentration caused by microjets formed in the vicinity of the electrode at elevated ultrasonic intensities. • The competition between acoustic streaming and the cavitation effect explains the trend of the behavior of the electrochemical parameters at intermediate ultrasonic intensities. The electrochemical deposition and dissolution of Cu from chloride-based electrolyte was studied employing the electrochemical quartz crystal microbalance (EQCM)-coupled ultrasound technique. The ultrasound was generated using an ultrasonic horn probe, which was positioned in the face-on configuration at a different distance (8, 15, and 22 mm) from the quartz. Small intensities of ultrasound (up to ca. 11–13 W cm −2 ) caused a significant enhancement of anodic, cathodic currents, as well as the amount of deposited Cu paralleled by an increase in the current efficiencies due to the enhanced mass transport caused by ultrasound acoustic streaming. A further increase in the ultrasonic intensity continuously decreased the amount of Cu deposited as well as the calculated current efficiencies where the ultrasound acoustic cavitation (favor ablation) becomes more important and overtakes the effect of acoustic streaming. The peculiarities in sonoelectrochemistry at intermediate intensities ( ca. 25 W cm −2 ) could be explained by a competition between the two effects. In agreement with the literature, the Cu corrosion reaction is occurring in parallel to its anodic dissolution with a corrosion rate increasing with increasing the ultrasound intensity. At the horn-quartz distance of 8 mm and intensity of 76 W cm −2 limits of the EQCM application (in the ultrasound field) were reached and the Cu deposition could not take place.